Follow the following steps:
1. Get SP flash tools (Latest version)
2. Download your phone's firmware (from manufacturer site or needrom.com etc) and extract it.
3. install Mediatek Preloader drivers as per your OS version (win x7 , 8 10 etc) and architecture (32/64bit).
4. Run Flash tools with admin as administrator
5. select the scatter file from the firmware folder you downloaded and wait for it to load. (Do not connect your phone yet and leave the battery inserted)
6. Select Download Only
7. Hit the download button
8. Now plug in the micro/type C usb end of your cable to your phone but dont plug to PC. yet
9. While hold down both volume buttons i.e up and down buttons, (Do not press the power button), Insert the Usb cable end to your PCs usb port (Please choose a port thats very reliable).
10. After a while, P Flash tool will begin to upgrade your phone, dont release the buttons yet, let it lapse about 2mins then release them, the firmware upgrade will still continue and it will display a tick pop-up when done (this may take between 5-10mins).
Now unplug your phone, remove and re-insert the battery and power-up your phone. You phone is now unbricked.
Note that the first boot will longer than a regular boot.